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<a name="PowerPC-ELF32"></a>
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<p>
Next: <a href="PowerPC64-ELF64.html#PowerPC64-ELF64" accesskey="n" rel="next">PowerPC64 ELF64</a>, Previous: <a href="Nios-II.html#Nios-II" accesskey="p" rel="prev">Nios II</a>, Up: <a href="Machine-Dependent.html#Machine-Dependent" accesskey="u" rel="up">Machine Dependent</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="ld-and-PowerPC-32_002dbit-ELF-Support"></a>
<h3 class="section">4.12 <code>ld</code> and PowerPC 32-bit ELF Support</h3>
<a name="index-PowerPC-long-branches"></a>
<a name="index-_002d_002drelax-on-PowerPC"></a>
<p>Branches on PowerPC processors are limited to a signed 26-bit
displacement, which may result in <code>ld</code> giving
&lsquo;<samp>relocation truncated to fit</samp>&rsquo; errors with very large programs.
&lsquo;<samp>--relax</samp>&rsquo; enables the generation of trampolines that can access
the entire 32-bit address space.  These trampolines are inserted at
section boundaries, so may not themselves be reachable if an input
section exceeds 33M in size.  You may combine &lsquo;<samp>-r</samp>&rsquo; and
&lsquo;<samp>--relax</samp>&rsquo; to add trampolines in a partial link.  In that case
both branches to undefined symbols and inter-section branches are also
considered potentially out of range, and trampolines inserted.
</p>
<a name="index-PowerPC-ELF32-options"></a>
<dl compact="compact">
<dd><a name="index-PowerPC-PLT"></a>
<a name="index-_002d_002dbss_002dplt"></a>
</dd>
<dt><samp>--bss-plt</samp></dt>
<dd><p>Current PowerPC GCC accepts a &lsquo;<samp>-msecure-plt</samp>&rsquo; option that
generates code capable of using a newer PLT and GOT layout that has
the security advantage of no executable section ever needing to be
writable and no writable section ever being executable.  PowerPC
<code>ld</code> will generate this layout, including stubs to access the
PLT, if all input files (including startup and static libraries) were
compiled with &lsquo;<samp>-msecure-plt</samp>&rsquo;.  &lsquo;<samp>--bss-plt</samp>&rsquo; forces the old
BSS PLT (and GOT layout) which can give slightly better performance.
</p>
<a name="index-_002d_002dsecure_002dplt"></a>
</dd>
<dt><samp>--secure-plt</samp></dt>
<dd><p><code>ld</code> will use the new PLT and GOT layout if it is linking new
&lsquo;<samp>-fpic</samp>&rsquo; or &lsquo;<samp>-fPIC</samp>&rsquo; code, but does not do so automatically
when linking non-PIC code.  This option requests the new PLT and GOT
layout.  A warning will be given if some object file requires the old
style BSS PLT.
</p>
<a name="index-PowerPC-GOT"></a>
<a name="index-_002d_002dsdata_002dgot"></a>
</dd>
<dt><samp>--sdata-got</samp></dt>
<dd><p>The new secure PLT and GOT are placed differently relative to other
sections compared to older BSS PLT and GOT placement.  The location of
<code>.plt</code> must change because the new secure PLT is an initialized
section while the old PLT is uninitialized.  The reason for the
<code>.got</code> change is more subtle:  The new placement allows
<code>.got</code> to be read-only in applications linked with
&lsquo;<samp>-z relro -z now</samp>&rsquo;.  However, this placement means that
<code>.sdata</code> cannot always be used in shared libraries, because the
PowerPC ABI accesses <code>.sdata</code> in shared libraries from the GOT
pointer.  &lsquo;<samp>--sdata-got</samp>&rsquo; forces the old GOT placement.  PowerPC
GCC doesn&rsquo;t use <code>.sdata</code> in shared libraries, so this option is
really only useful for other compilers that may do so.
</p>
<a name="index-PowerPC-stub-symbols"></a>
<a name="index-_002d_002demit_002dstub_002dsyms"></a>
</dd>
<dt><samp>--emit-stub-syms</samp></dt>
<dd><p>This option causes <code>ld</code> to label linker stubs with a local
symbol that encodes the stub type and destination.
</p>
<a name="index-PowerPC-TLS-optimization"></a>
<a name="index-_002d_002dno_002dtls_002doptimize"></a>
</dd>
<dt><samp>--no-tls-optimize</samp></dt>
<dd><p>PowerPC <code>ld</code> normally performs some optimization of code
sequences used to access Thread-Local Storage.  Use this option to
disable the optimization.
</p></dd>
</dl>



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